1. Field of the Invention
The present invention relates to optical disc apparatus for playback from or recording to optical discs, and more particularly relates to optical disc apparatus that can suppress erroneous detection of tracking failures.
2. Description of Related Art
Today, optical discs such as CDs (compact discs) and DVDs (digital versatile discs) are popular and widely used. For the recording and playback of information, such as audio and video information, to and from optical discs, optical disc apparatus are available. Well-known optical disc apparatus include, among others, CD players, DVD players, and CD-ROM drives connected to personal computers.
An optical disc apparatus is provided with an optical pickup for irradiating an optical disc with a light beam to read information. The optical pickup shines the optical beam onto the information recording surface of the optical disc, which is fixed to a turntable and is being rotated.
The light reflected from the information recording surface is received by a photodetector, for example a photodiode, provided inside the optical pickup. The photodetector converts the light into an electrical signal and, based on the thus obtained electrical signal, outputs the information recorded on the optical disc.
Accurate reading of information from the optical disc requires operation whereby the optical axis of the light beam is made to follow the center of a sequence of pits (tracking operation). For that purpose, the optical pickup incorporates an actuator for driving an objective lens in the radial direction of the optical disc and a tracking servo for controlling the actuator.
In this connection, there have been proposed devices that generate a binarized track cross signal to detect tracking failures wherein the conditions for a retry on detection of a tracking failure are eased for reliable detection of extraneous vibration and impact (see, for example, JP-A-2006-164335).
Inconveniently, however, with the conventional technology like that mentioned above, if an optical disc has, due to its physical properties etc., a spot at which the binarized track cross signal tends to rise, a tracking failure may be detected erroneously, causing the tracking servo to be turned off.
Once this happens, even when a retry operation is executed to track on again, it is highly likely that a similar fault immediately occurs, leading to repeated retries resulting in failure to read. Consequently, during the playback etc. of the optical disc, servo deviations occur frequently, causing failure to mount and halts in video during playback.